The delivery of radio frequency (RF) energy to target regions within solid tissue is known for a variety of purposes of particular interest to the present invention. In one particular application, RF energy may be delivered to diseased regions (e.g., tumors) for the purpose of ablating predictable volumes of tissue with minimal patient trauma.
In a typical procedure, tissue suspected of containing an abnormality is imaged using a high definition imaging modality, such as Magnetic Resonance Imaging (MRI). If an abnormality, such as a tumor, is discovered, a sample of the abnormal tissue is retrieved. This is typically accomplished by percutaneously introducing a biopsy needle through healthy tissue into contact with the abnormal tissue. Proper guidance and placement of the biopsy needle is facilitated by the use of a standard imaging modality, such as fluoroscopy. The biopsy needle, with the tissue sample, is then removed from the patient's body, and the tissue sample is placed into a container and sent to a laboratory to examine whether it is malignant or benign. In the interim, the physician and/or patient may decide to treat the tumor, whether or not the tumor is actually malignant or benign. In this case, the abnormal tissue would typically be treated immediately after performing the biopsy. Alternatively, the physician and/or patient may decide to treat the tumor only if it is indeed malignant, in which case, such malignancy would be treated after receiving the laboratory results.
In either case, the tumor can be treated by percutaneously introducing an RF ablation probe through the patient's body into contact with the tumor in a similar manner that the biopsy needle was described above. The ablation probe can then be operated to ablate the tumor. The interstitial space left by the removal of the tumor can then be treated with a therapeutic agent, such as a drug. Typically, this is accomplished by introducing a separate drug delivery device into the patient's body in the same manner as the biopsy needle and ablation probe was, and delivering the drug into the interstitial space.
RF ablation of tumors is currently performed using one of two core technologies. The first technology uses a single needle electrode, which when attached to a RF generator, emits RF energy from the exposed, uninsulated portion of the electrode. This energy translates into ion agitation, which is converted into heat and induces cellular death via coagulation necrosis. The second technology utilizes multiple needle electrodes, which have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. U.S. Pat. No. 6,379,353 discloses such a probe, which comprises a delivery cannula and an electrode deployment member reciprocatably mounted within the delivery cannula to alternately deploy an electrode array from the delivery cannula and retract electrode array within the delivery cannula. The individual electrodes within the array have spring memory, so that they assume a radially outward, arcuate configuration as they are deployed from the delivery cannula. In general, a multiple electrode array creates a larger lesion than that created by a single needle electrode.
When creating lesions using ablation electrode element (whether a single needle electrode or needle electrode array, deployable or otherwise) RF energy is commonly delivered to the tissue in one of several ways. In one arrangement, RF current may be delivered to an ablation electrode element in a monopolar fashion, which means that current will pass from the ablation electrode element to a dispersive electrode attached externally to the patient, e.g., using a contact pad placed on the patient's flank. In another arrangement, the RF current is delivered to two electrodes in a bipolar fashion, which means that current will pass between “positive” and “negative” electrodes in close proximity to each other, e.g., two electrodes on the same probe or array. Bipolar arrangements, which require the RF energy to traverse through a relatively small amount of tissue between the tightly spaced electrodes, are more efficient than monopolar arrangements, which require the RF energy to traverse through the thickness of the patient's body. As a result, bipolar electrode arrays generally create larger and/or more efficient lesions than monopolar electrode arrays. Additionally, bipolar arrangements are generally safer for the physician and patient, since there is an ever-present danger that the physician and patient may become a ground in the monopolar arrangement, resulting in painful burns.
Although the current treatment of tumors is generally successful, there is still room for improvement. For example, even though such treatments can be considered minimally invasive in that open surgery is not required, they still require multiple instrument insertions during the biopsy, ablation, and drug delivery steps—causing tissue trauma with each insertion. Notably, even if the biopsy needle, ablation probe, and drug delivery device are introduced through the same opening in the skin, they will tend to take different tissue paths to the tumor. In addition, the patient must be imaged each time an instrument is guided through the patient's body into contact with the tumor. As such, the patient may have to be imaged several times during biopsy, ablative treatment, and drug delivery. Also, even though tumors come in all shapes and sizes, lesions resulting from a particular bipolar arrangement will typically have the same geometry, since the electrodes that make up a typical bipolar arrangement are fixed relative to each other. As such, some tumors may not be efficiently ablated using a standard bipolar ablation probe.
Thus, there is a need for a tumor treatment kit and method that minimizes the number of instruments that must be inserted into the patient's body and provides for a more efficient bipolar ablation of the tumor.